Nucleated casting systems and methods comprising the addition of powders to a casting

Abstract

Nucleated casting systems and methods comprise the addition of powders into a liquidus portion of the casting. The casting system forms a casting comprising a liquidus portion that receives the refined liquid metal and a solidified portion, the casting further comprising a fine-grain, homogeneous microstructure that is essentially oxide- and sulfide-free and segregation defect free. The casting system comprises a source of refined liquid metal, the refined liquid metal having oxides and sulfides refined out of the metal; a solid metal particle addition system that adds solid metal particles to a surface of the liquidus portion of the casting; and a nucleated casting system for forming the casting. The solid metal particle addition system adds solid metal particles that serve as nucleation centers during solidification of the casting.

We claim:  
     
       1. A casting system having solid metal particle addition, the casting system forming a casting that comprises a semi-solid portion that receives a stream of a refined liquid metal and a solidified portion, the casting further comprising a fine-grain, homogeneous microstructure that is essentially oxide-free and sulfide-free and is segregation defect free, the casting system comprising: 
       a source of the refined liquid metal, wherein oxides and sulfides have been refined out of the refined liquid metal, and wherein the source provides the stream of the refined liquid metal to the casting;  
       a solid metal particle addition system metal that adds solid metal particles to a surface of the semi-solid portion of the casting such that the solid metal particles are dispersed atop the surface of the semi-solid portion, wherein the solid metal particle addition system is separate from the source of refined liquid metal; and  
       a nucleated casting system for forming the casting, wherein the nucleated casting system is adapted to receive both the solid metal particles and the stream of refined liquid metal to form the casting that comprises a fine-grain, homogeneous microstructure that is essentially oxide-free and sulfide-free and is segregation defect free,  
       wherein the solid metal particle addition system adds the solid metal particles that serve as nucleation centers during solidification of the casting. 
     
     
       2. The casting system according to  claim 1 , wherein the source of refined liquid metal comprises an electroslag refining system. 
     
     
       3. The casting system according to  claim 2 , wherein the electroslag refining system comprises: 
       an electroslag refining structure that is adapted for the electroslag refining of the source of refined liquid metal and providing molten slag;  
       a cold hearth structure for holding a refined molten metal beneath the molten slag and providing refined molten metal in the cold hearth structure;  
       a source of raw metal for insertion into the electroslag refining structure and into contact with the molten slag in the electroslag refining structure to form the source of refined liquid metal;  
       an electrical power supply adapted to supply electric power to electroslag refine the source of raw metal through a circuit, the circuit comprising the power supply, the source of raw metal, the molten slag and the electroslag refining structure sufficient for resistance melting the source of raw metal where the source of raw metal contacts the molten slag and forming molten droplets of refined liquid metal;  
       an outlet for allowing the molten droplets to fall through the molten slag;  
       a collector for collecting the molten droplets after they pass through the molten slag as a body of refined liquid metal in the cold hearth structure directly below the electroslag refining structure; and  
       a cold finger orifice structure having an orifice at the lower portion of the cold hearth structure for draining the electroslag refined metal that collects in the cold hearth orifice structure through the orifice of the cold finger orifice structure.  
     
     
       4. The casting system according to  claim 3 , wherein the source of metal comprises an alloy selected from at least one of nickel-, cobalt-, titanium-, or iron-based metals, and the casting formed by the casting process comprises at least one of nickel-, cobalt-, titanium-, or iron-based metals. 
     
     
       5. The casting system according to  claim 3 , wherein a rate of advance of the source of metal into the refining structure corresponds to the rate at which a lower end of the ingot is melted by the resistance melting. 
     
     
       6. The casting system according to  claim 3 , wherein the orifice forms a stream of molten metal. 
     
     
       7. The casting system according to  claim 3 , wherein the electroslag refining structure and the cold hearth structure comprise upper and lower portions of the same structure. 
     
     
       8. The casting system according to  claim 3 , wherein the electrical power supply comprises a circuit formed in the refined liquid metal. 
     
     
       9. The casting system according to  claim 3 , wherein the orifice establishes a drainage rate that is approximately equivalent to a rate of resistance melting. 
     
     
       10. The casting system according to  claim 1 , wherein the nucleated casting system further comprises: 
       a mold for collecting and solidifying metal from the source, in which a turbulent zone is generated at an upper surface of the mold and, the turbulent zone on average is solidified less than about 50% by volume.  
     
     
       11. The casting system according to  claim 10 , wherein the turbulent zone on average is solidified about 5% to about 40% by volume. 
     
     
       12. The casting system according to  claim 1 , wherein the casting comprises at least one of a casting, ingot, and preform. 
     
     
       13. The casting system according to  claim 1 , wherein the casting comprises at least one of nickel-, cobalt-, titanium-, or iron-based metals. 
     
     
       14. The casting system according to  claim 1 , wherein the casting is capable for use in turbine component applications. 
     
     
       15. The casting system according to  claim 1 , wherein the source of refined liquid metal is selected from at least one of a consumable electrode, a powdered source of metal, and melt source of metal. 
     
     
       16. The casting system according to  claim 1 , wherein the solid metal particle addition system comprises: 
       at least one source of solid metal particles and at least one dispersion system that permits solid metal particles to exit the solid metal particle addition system and be fed to the casting.  
     
     
       17. The casting system according to  claim 1  further comprising a controlled atmosphere environment, wherein the solid metal particle addition system being within the controlled atmosphere environment. 
     
     
       18. The casting system according to  claim 1  further comprising a controlled atmosphere environment, wherein the solid metal particle addition system is partially within the controlled atmosphere environment. 
     
     
       19. The casting system according to  claim 17 , wherein the solid metal particle addition system comprises a source of solid metal particles, the source of solid metal particles is partially within the controlled atmosphere environment. 
     
     
       20. The casting system according to  claim 18 , wherein the solid metal particle addition system comprises a source of solid metal particles, the source of solid metal particles is partially within the controlled atmosphere environment. 
     
     
       21. The casting system according to  claim 20 , wherein the source of solid metal particles comprises an atomization system that forms solid metal particles from liquefied metal, in which the solid metal particles are fed to the casting from the atomization system. 
     
     
       22. The casting system according to  claim 20 , wherein the source of solid metal particles comprises a receptacle having solid metal particles therein, in which the solid metal particles are fed to the casting from the receptacle. 
     
     
       23. The casting system according to  claim 20 , wherein the source of solid metal particles comprises a rotating source of solid metal particles for feeding solid metal particles to the casting. 
     
     
       24. The casting system according to  claim 20 , wherein the source of solid metal particles comprises an arcuate configuration for feeding solid metal particles to the casting. 
     
     
       25. The casting system according to  claim 1 , wherein the solid metal particle addition system comprises at least one dispersion assisting system that facilitates addition of the solid metal particles to the semi-solid portion of the casting. 
     
     
       26. The casting system according to  claim 25 , wherein the dispersion assisting system is selected from at least one of: 
       a vibrating dispersion assisting device, a gas jet dispersion assisting device, a magnetic dispersion assisting device, a shaker dispersion assisting device, and combinations thereof.  
     
     
       27. A casting method with solid metal particle addition provided to a casting that is formed by the casting method, the casting comprising a semi-solid portion that receives a stream of a refined liquid metal and a solidified portion, the casting further comprising a fine-grain, homogeneous microstructure that is essentially oxide-free and sulfide-free and is segregation defect free, the casting method comprising: 
       providing a source of the refined liquid metal, the refined liquid metal having oxides and sulfides refined out of the metal;  
       supplying the source of refined liquid metal to a nucleated casting system;  
       forming a casting by nucleated casting in the nucleated casting system, the casting comprising a semi-solid portion and a solidified portion; and  
       adding solid metal particles to an exposed surface of the semi-solid portion;  
       wherein solid metal particles serve as nucleation centers during solidification. 
     
     
       28. The method according to  claim 27 , wherein the step of providing a source of refined liquid metal comprises electroslag refining, the step of electroslag refining comprises: 
       providing a source of the refined liquid metal to be refined;  
       providing an electroslag refining structure adapted for the electroslag refining of the source of refined liquid metal and providing molten slag in the vessel;  
       providing a cold hearth structure for holding a refined molten metal beneath the molten slag and providing refined molten metal in the cold hearth structure;  
       mounting the source of refined liquid metal for insertion into the electroslag refining structure and into contact with the molten slag in the electroslag refining structure;  
       providing an electrical power supply adapted to supply electric power;  
       supplying electric power to electroslag refine the source of refined liquid metal to form refined liquid metal in the form of molten droplets through a circuit, the circuit comprising the power supply, the source of metal, the molten slag and the electroslag refining structure;  
       resistance melting of the source of metal where the source of metal contacts the molten slag and forming molten droplets of metal;  
       allowing the molten droplets to fall through the molten slag;  
       collecting the molten droplets after they pass through the molten slag as a body of refined liquid metal in the cold hearth structure directly below the electroslag refining structure;  
       providing a cold finger orifice structure having a orifice at the lower portion of the cold hearth structure; and  
       draining the electroslag refined metal that collects in the cold hearth orifice structure through the orifice of the cold finger orifice structure.  
     
     
       29. The method according to  claim 28 , wherein the source of refined liquid metal comprises an alloy selected from at least one of nickel-, cobalt-, titanium-, or iron-based metals, and the casting formed by the nucleated casting method comprises at least one of nickel-, cobalt-, titanium-, or iron-based metals. 
     
     
       30. The method according to  claim 28 , wherein a rate of advance of the source of refined liquid metal into the refining structure corresponds to the rate at which of resistance melting. 
     
     
       31. The method according to  claim 28 , wherein the step of draining comprises forming a stream of molten metal. 
     
     
       32. The method according to  claim 28 , wherein the electroslag refining structure and the cold hearth structure comprise upper and lower portions of the same structure. 
     
     
       33. The method according to  claim 28 , wherein the step of supplying electric power comprises forming a circuit in the refined liquid metal. 
     
     
       34. The method according to  claim 28 , wherein the step of draining comprises establishing a drainage rate that is approximately equivalent to a rate of resistance melting. 
     
     
       35. The method according to  claim 28 , wherein the step of forming a casting further comprises: 
       forming a stream of refined liquid metal; and  
       collecting and solidifying the stream in a mold for forming the casting by the step of nucleated casting, in which a turbulent zone is generated by the stream at an upper surface thereof and, wherein the step of collecting and solidifying, on average solidifies less than about 50% by volume of the stream.  
     
     
       36. The method to  claim 27 , wherein the step of adding solid metal particles to a surface of the semi-solid portion comprises: 
       adding solid metal particles from a source and dispersing the solid metal particles with a dispersion system that permits solid metal particles to be fed to the casting.  
     
     
       37. The method according to  claim 27 , wherein the step of adding solid metal particles to a surface of the semi-solid portion comprises adding the solid metal particles in a controlled atmosphere environment. 
     
     
       38. The method according to  claim 27 , wherein the step of adding solid metal particles to a surface of the semi-solid portion comprises forming solid metal particles from liquefied metal in an atomization system. 
     
     
       39. The method according to  claim 27 , wherein the step of adding solid metal particles to a surface of the semi-solid portion comprises feeding solid metal particles from a receptacle to the casting. 
     
     
       40. The method according to  claim 27 , wherein the step of adding solid metal particles to a surface of the semi-solid portion comprises rotating a source of solid metal particles to add the solid metal particles over a surface of the semi-solid portion of the casting. 
     
     
       41. The method according to  claim 27 , wherein the step of adding solid metal particles to a surface of the semi-solid portion comprises dispersing the solid metal particles to the semi-solid portion of the casting. 
     
     
       42. The method according to  claim 41 , wherein the step of adding solid metal particles to a surface of the semi-solid portion further assisting the dispersion of solid metal particles to the semi-solid portion by at least one of: 
       vibrating, dispersing with a gas jet, dispersing with a magnet, shaking, and combinations thereof.  
     
     
       43. A casting method comprising: 
       electroslag refining a metal electrode to produce a refined molten stream;  
       cooling said stream to establish a solid volume fraction portion thereof up to a viscosity inflection point;  
       collecting said stream in a mold to form a liquid metal pool therein;  
       dispersing solid metal particles atop an exposed surface of said pool to provide nuclei therein;  
       extracting heat from said mold to solidify said pool in a solidified portion of said casting having a semi-solid portion thereatop; and  
       solidifying said pool at said nuclei to form a solidified casting therein.  
     
     
       44. A method according to  claim 43  wherein said particles comprise metal powder. 
     
     
       45. A method according to  claim 43  further comprising atomizing a liquified metal to form said particles. 
     
     
       46. A method according to  claim 43  further comprising rotating distribution of said particles for dispersion thereof over said semi-solid surface. 
     
     
       47. A method according to  claim 43  wherein said particles are dispersed over said semi-solid surface from a plurality of sources. 
     
     
       48. A method according to  claim 43  further comprising retracting said casting from said mold as said mold fills with metal solidified from said semi-solid portion. 
     
     
       49. A method according to  claim 48  further comprising rotating said casting for rotating said semi-solid portion and dispersing said particles thereatop.